Block copolymers have been developed rapidly within the recent past, the starting monomers usually being monoalkenyl arenes such as styrene or alphamethyl styrene block polymerized with conjugated dienes such as butadiene and isoprene. A typical block copolymer of this type is represented by the structure polystyrene-polybutadiene-polystyrene. When the monoalkenyl arene blocks comprise less than about 55% by weight of the block copolymer, the product is essentially elastomeric. Moreover, due to their peculiar set of physical properties they can be referred to more properly as thermoplastic elastomers. By this is meant polymers which in the melt state are processable in ordinary thermoplastic processing equipment but in the solid state behave like chemically vulcanized rubber without chemical vulcanization having been effected. Polymers of this type are highly useful in that the vulcanization step is eliminated and, contrary to scrap from vulcanized rubbers, the scrap from the processing of thermoplastic elastomers can e recycled for further use. The oxidative stability of such block copolymers is improved by selective hydrogenation of the diene blocks without hydrogenation of the styrene blocks. Such block copolymers are described in U.S. Pat. No. Re. 27,145 and U.S. Pat. No. 3,595,942.
These hydrogenated block copolymers have enjoyed broad commercial success. Nevertheless, improvements in such polymers are desired. In particular, for particular applications such particular polymers require greater solvent resistance and higher use temperature. Still further, such polymers also need improved adhesion to polar materials when used in certain blend compositions. What has now been discovered is a new block copolymer that overcomes these deficiencies.